1. Field of the Invention
The present invention relates to an apparatus for validating authenticity features on documents of value and security documents, in particular bank notes which pass through a testing apparatus in a batch processing mode, wherein a detector device detects the authenticity feature and supplies the authenticity feature to a signal processing device.
2. Description of the Related Art
A device of the afore-described type is disclosed, for example, in EP 0 633 533 B1 or EP 0 477711 B1.
Both devices are implemented as so-called bank note testing devices which are capable of testing a large number of bank notes within a relatively short time in continuous operation.
The references cited above, however, are disadvantageously based on image recognition which is time-consuming. This adversely affects the processing capability of such testing devices. In fact, complete images are recognized, i.e., symbols are detected and compared with stored symbols. This requires a decrease in the transport speed during symbol recognition and evaluation so as to allow sufficient computing time for the evaluation and a pass-fail decision.
Moreover, with conventional symbol recognition only visible symbols are detected which is no longer adequate considering the present state of the technology for testing the authenticity of bank notes.
It is a therefore an object of the invention to improve an apparatus of the aforedescribed type for validating authenticity features so that invisible authenticity features can also be evaluated and processed with high quality at significantly greater transport speeds.
The present invention provides for a system including a detection device which is capable of detecting the electroluminescent properties of the authenticity features in a document of value, security document, bank note, personal document or plastic card. It is an important feature of the invention that the detected electroluminescent properties of authenticity features can be evaluated.
In this way, the apparatus is no longer limited to recognizing optically visible authenticity features, but can also detect and evaluate invisible authenticity features, in particular authenticity features that have electroluminescence properties.
As described in other applications assigned to the same applicant, bank notes can be provided with electroluminescent features. However, it has hitherto not been known to evaluate such authenticity features in automatic testing devices at a high processing speed.
According to a preferred embodiment of the invention, the detector device includes at least two opposing electrodes, with the security document and document of value to be tested moving between the opposing electrodes, with at least one detector capable of detecting the electroluminescence signal of the authenticity features and converting the electroluminescence signal into an electrical signal.
The term xe2x80x9celectroluminescencexe2x80x9d refers to all phosphorescent and fluorescent elements which produce a corresponding luminescence signal under the influence of an alternating electromagnetic field. This signal need not necessarily be located in the visible spectral range. It can also be located in the IR or UV spectral range; but it can also be located in the visible spectrum. Moreover, the luminescence signal can be located both in the visible and in the invisible spectral range, with the associated detector device capturing and processing this signal.
For producing an alternating electromagnetic field with the frequency approaching several MHz, the alternating electromagnetic field has to penetrate the security document and document of value at the location where the authenticity signal is to be tested. For this purpose, the alternating electromagnetic field is coupled into the security document and document of value. The coupling is preferably capacitive, i.e., the security document and document of value is guided in the field gap between two mutually opposing electrodes, with the respective poles of the electrodes being connected to the signal source to produce the alternating electromagnetic field.
The air gap between the electrodes and the document of value and security document should be as small as possible so as to provide the best possible interaction between the alternating electromagnetic field and the security document and document of value. Preferably, at least one of the electrodes is resiliently pressed against the security document and document of value, so thatxe2x80x94by minimizing the air gapxe2x80x94the electric field strength penetrating the security document and document of value is as high as possible.
Such electrodes can be implemented in several ways:
In one embodiment, one of the electrodes can be a two-dimensional electrode, whereas in the other electrode can be formed as a resiliently biased roller placed opposite the two-dimensional electrode. The resilient bias can be produced by resiliently pretensioning the axle of the pressure roller in the transport plane of the document of value and security document, so that the pressure roller resiliently contacts one side of the document of value and security document, whereas the other side of the document of value and security document or bank note contacts the opposing two-dimensional electrode.
The emitted luminescence signal can advantageously be detected by making the two-dimensional electrode transparent for the emitted luminescence signal and by placing the detector device for capturing the luminescence signal on the other side of this electrode. However, the invention is not limited to this embodiment.
In another embodiment of the invention, both electrodes can be formed by respective pressure rollers, wherein at least one of the pressure rollers is pretensioned in the transport plane of the document of value and security document.
In the present and in the preceding embodiment, the cylindrical electrode which is formed as a pressure roller, is assumed to have a conductive coating that is coupled to one pole of the alternating field generator. This can be accomplished by connecting the coating of the pressure roller electrically with the axle of the pressure roller, wherein the axle is pretensioned and electrically isolated from a resiliently biased pressure device. The signal to be coupled to the coating can then be transmitted to the axle via a slip ring contact and transmitted from there to the coating.
In a third embodiment of the invention, two two-dimensional electrodes are provided, wherein at least one of the two-dimensional electrodes is resiliently biased against the other electrode. In this way, the alternating electromagnetic field can penetrate the bank note that is introduced into the gap between the electrodes without any intervening air gap.
To simplify the setup, at least one of the two-dimensional electrodes is preferably transparent for the luminescence signal. If the luminescence signal is at least partially in the visible spectral range, then at least one of the electrodes is formed of a transparent electrically conductive material (e.g., indium tin oxide), which can furthermore be colored like, for example, a filter disk so as to transmit a narrow band of the captured luminescence signal to the detector located on the other side of the transparent electrode.
However, if the emitted luminescence signal is in the invisible spectral range, then at least the one electrode needs to be transparent only for the spectral range of the luminescence signal and can be opaque in the visible spectral range.
The detector device can located so as to detect only a predetermined track on the bank note to be tested. Alternatively, several detector devices can be arranged side by side, or a detector device can have two detectors for evaluating the luminescence signal. With the latter embodiment, only the difference signal is advantageously evaluated which is unaffected by external parameters (for example, temperature fluctuations, ambient humidity, and moisture in the security document and document of value).
Forming the difference between two detector devices hence increases the reliability for evaluating the detected luminescence signal.
The invention will hereinafter be described a greater detail with reference to the drawings which illustrate several embodiments. Additional features and advantages of the invention which are important for the invention, will become clearer from the drawings and the description.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are intended solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims.